Wireless networks and wireless local area networks (WLANs) are becoming increasingly common and are forming an increasingly vital part of global networks. The typical WLAN has one or more access points (APs) that broadcast and receive wireless signals from the wireless network. On a typical corporate campus, the intent is to provide wireless coverage for the central buildings of the campus while minimizing signal drift (i.e., “bleed”) outside of the geographic boundaries of the campus property.
A typical access point generates a radio frequency signal in a spherical distribution. Users near the center of the sphere (i.e., closest to the access point) will receive the strongest signal. However, the signal strength decays as users move towards the periphery of the sphere. In an ideally secure campus, the signal dies out altogether before it reaches the physical boundaries of the property on which the campus is located. This would help to prevent unauthorized users (i.e., attackers) from driving by outside of the campus property and intercepting confidential wireless signals.
Unfortunately, WLAN radiation zones have a tendency to spill over or “bleed” radio frequency broadcasts beyond the defined, allowable perimeter of campus properties. This is extremely dangerous, because unauthorized users can walk or drive by (while remaining safely outside of the property) and can intercept private data transmissions from the campus WLAN. Such unauthorized users are commonly known as “wardrivers.” Wardriving can be performed my malicious users who want to surreptitiously eavesdrop or spy on private WLAN communications through radio frequency transmissions over a distance. Thus, it is vital to be able to minimize signal “bleed” at the boundaries of the property. This will keep the signal within an acceptable (i.e., secure) physical perimeter, thus helping to protect against wardrivers.
In the prior art, the only way to measure signal bleed is for a user to physically walk around the perimeter of the property and to measure signal strength at each point on the perimeter, by hand, using a mobile computing device and the appropriate software. Software such as Netstumbler and Kismet already exists to perform such a task. Unfortunately, the prior art suffers from several drawbacks. For example, because of electromagnetic interference, signal strength on the perimeter (i.e., bleed) is not static, but rather constantly waxes and wanes, like the ebb and flow of ocean tides. Thus, by the time the signal is measured by hand and recorded in the prior art, the signal may have already changed. In addition, environmental conditions affect signal bleed. For example, weather changes will cause the signal bleed to wax and wane with time.
Furthermore, in wireless local networks there is a need to regulate the power transmitted by an antenna in a particular direction. For example, existing software-controlled directional antenna can selectively beam data in different directions, depending on where the client (i.e., the target user's device) is located at that particular time. In this case, it would be advantageous for the directional antenna to send only enough power in a particular direction to serve the client's requirements. Such an optimization would improve efficiency by reducing overall power consumption by the antenna. It would also limit RF interference in the local neighborhood by providing just enough power to serve a client's needs, and only in the direction of the client's location.
In addition, wireless “mesh” networks are becoming more more prevalent. In a mesh network, various wireless devices of all types (such as laptops, cellphones, etc.) can automatically interconnect with one another when they are within a certain range. The mesh network can grow larger or smaller depending on how many devices are connected at the periphery of the mesh. In this case, it would advantageous to limit signal strength between individual “nodes”, or devices, in the mesh. By limiting signal strength of each node to the minimum level required to communicate with one or more of its neighbors, RF interferences of the mesh as a whole is reduced. Furthermore, limiting signal strength in a particular direction would further optimize the power efficiency and security of the wireless mesh network.
Currently, the prior art has no provision for automatically and flexibly adjusting perimeter RF signal bleed or directional signal strength in real time. Thus, power consumption is not optimized, and interference between devices can occur. In addition, uncontrolled, excessive signal bleed that changes over time and can subject the WLAN to interception and attacks from outside, malicious wardrivers.